This invention relates to axial gap electrical machines, and more particularly relates to such machines employing permanent magnets.
Axial gap electrical machines have been proposed in the past. One example is found in U.S. Pat. No. 5,619,087 (Sakai, issued Apr. 8, 1997). According to the FIG. 9 embodiment, central windings 35A are part of the stator which surround a metal rotor shaft (Col. 8, lines 55-58) and which are molded with epoxy resin (Col. 8, lines 2-3). Back yokes 36-1 and 36-2, which are part of the stator, are formed of strip silicon steel (Col. 8, lines 6-11) and are fixed between an outer ring 36b and an inner ring 36a (FIG. 12). The back yokes are displaced from permanent magnets 30a by an air gap 38-1 and additional coils 35-B.
Additional patents showing various forms of axial gap machines are described in U.S. Pat. No. 4,278,927 (Grohe, issued Jul. 14, 1981) and U.S. Pat. No. 5,245,238 (Lynch et al., issued Sep. 14, 1993).
The present invention has application as an electric wheel motor. Wheel motors are described in U.S. Pat. No. 5,450,915 (Li, issued Sep. 19, 1995), U.S. Pat. No. 5,633,544 (Toida et al., issued May 27, 1997), U.S. Pat. No. 4,330,045 (Myers, issued May 18, 1982), U.S. Pat. No. 4,109,741 (Gabriel, issued Aug. 29, 1978), U.S. Pat. No. 4,799,564 (Iijima et al., issued Jan. 24, 1989), U.S. Pat. No. 5,322,141 (Brunner et al., issued Jun. 21, 1994), U.S. Pat. No. 5,272,938 (Hsu et al., issued Dec. 28, 1993) and U.S. Pat. No. 5,163,528 (Kawamoto et al., issued Nov. 17, 1992).
Although the electric machines described in the foregoing patents are useful for some applications, experience has shown that an improved axial gap machine can be created by departing from the design techniques taught in such patents and following the principles taught and claimed in this application.